Browsing by Subject "Edwards Aquifer"
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Item A Fractal Interpretation of Controlled-Source Helicopter Electromagnetic Survey Data Seco Creek, Edwards Aquifer, TX(2010-07-14) Decker, Kathryn T.The Edwards aquifer lies in the structurally complex Balcones fault zone and supplies water to the growing city of San Antonio. To ensure that future demands for water are met, the hydrological and geophysical properties of the aquifer must be well-understood. Fractures often occur in a power-law distribution. Fracture distribution plays an important role in determining electrical and hydraulic current flowpaths. The thesis research presents an evaluation of the controlled-source electromagnetic (CSEM) response for layered models with a fractured layer at depth described by the roughness parameter, BV, such that 0Item Beyond the Aquifer : planning for San Antonio's future water supply(2010-05) Laughlin, Nathan Daniel; Butler, Kent S.; Schuster, StefanThis report examines water supply planning issues in San Antonio, Texas. San Antonio is unique among large cities in the United States in that it relies almost exclusively on a single source, the Edwards Aquifer, for its water supply. Because San Antonio’s water demand is projected to outgrow the Aquifer’s capacity, the city must consider other options to extend and augment its current water supply. After describing the hydrogeology and water supply history of San Antonio, this report explains the multitiered water planning structure and current and future water needs for the city. It then studies and evaluates three short-to-mid term water supply options. By continuing to develop its already successful water conservation programs and water reclamation system, San Antonio can delay the need for more costly and environmentally impactful water supply options down the road, and wisely manage the resources it already draws from.Item Groundwater flow and recharge within the Barton Springs segment of the Edwards Aquifer, southern Travis and northern Hays Counties, Texas(2009-05) Hauwert, Nico Mark; Sharp, John Malcolm, 1944-The Barton Springs Segment, part of the karstic Edwards aquifer in Central Texas, is a Sole Source aquifer, is habitat to rare karst species, and provides water to a well-loved municipal swimming pool, yet its hydrogeologic properties remain insufficiently understood. For this study, the hydrogeologic characteristics of the Barton Springs Segment were investigated using several approaches, including mapping of hydrostratigraphic units and faults, measurement of upland infiltration, groundwater traces, and aquifer tests. The depositional environment, diagenesis, fracturing, down-dropped and dipping faulted blocks, and subsequent dissolution were determined to play important roles in controlling groundwater flow-path development within the Barton Springs Segment. In particular, downdropped fault blocks create groundwater gradients to the southeast that influence flow in the Edwards outcrop area. Upland internal drainage basins were found to be extremely efficient at conveying recharge to the underlying aquifer. The maturity of natural internal drainage sinkholes can be measured by its bowl volume, which grows in proportion to the catchment area it captures. A 19-hectare internal drainage basin, HQ Flat sinkhole, was monitored for rainfall, evapotranspiration, soil moisture, and discrete runoff to the cave drain. During a 505-day period, 5.5% of measured rainfall entered the cave drain as discrete recharge, 26% of measured rainfall infiltrated through soils on the slopes, and the remaining 68% was lost through evapotranspiration. This amount of upland infiltration is consistent with infiltration measurements in other karst areas and is much larger than the 1% upland recharge of rainfall that was previously estimated. A chloride mass balance indicates that at the adjacent Tabor research site, about 50% of rainfall infiltrates to a 6-meter depth. Dye-tracing and pump tests demonstrated that primary and secondary groundwater flow paths are the major influence on transmissivity within the Barton Springs Segment. Groundwater tracing breakthroughs reveal very high advection and relatively low dispersion. Drawdown response to pump tests indicates a very high degree of anisotropy, controlled by location of groundwater flow paths. Overall the Barton Springs Segment is a mature karst aquifer with highly developed rapid, discrete network for both recharge and groundwater-flow.Item Improvements and assessments of water auditing techniques(2009-05-15) Meyer, Sarah RuthWater auditing is an emerging method of increasing accountability for water utility systems. A water loss audit according to the methodology of the International Water Association (IWA) is applied to a major North American water utility, San Antonio Water System (SAWS), which is already a leader in conservation policies. However, some modifications to the auditing process are needed for this model?s application to a North American utility. These improvements to the IWA methodology include: calculating system input volume from multiple methods of measurements as well as numerous input points, incorporating deferred storage consumption (in this case aquifer storage and recovery) principles into the auditing process, calculating a volume of unavoidable annual real losses (allowable leakage) for a system with varied pressure zones, and defining procedures for assessing customer meter accuracy for a system. Application of the improved IWA audit method to SAWS discovered that its system input volume is being significantly undermeasured by current practices, current water loss control programs are very effective, customer accounting procedures result in large volumes of apparent loss, and current customer meter accuracy is adequate but could be marginally improved. Application of the audit process to the utility is beneficial because it facilitates increased communication between utility departments, assesses shortcomings in current policies, pin-points areas needing increased resources, and validates programs that are performing well.Item Modeling an endangered species in an urban landscape: fountain darter (Etheostoma fonticola) survival in the Upper San Marcos River, Hays County, Texas(2010-07-14) Wilkins, Leann I.To accommodate for human population growth along the Texas I-35 corridor, land is becoming increasingly urban and decreasingly pervious, modifying the infiltration and runoff rates in the Edwards Aquifer, especially to its spring fed Upper San Marcos River (USMR). Contaminants like heavy metals and organic chemicals can accumulate on impervious surfaces and with runoff, enter into the USMR at potentially harmful levels. The objective of this study was to determine how the population of an endangered Edwards Aquifer species, the fountain darter (Etheostoma fonticola), might respond to potential water quality changes associated with urbanization. I developed a stochastic, sex and stage-structured population dynamics simulation model that represents the relationships between urbanization, springflow variations, contamination levels, and natural history of the fountain darter. Future fountain darter population trends (2008-2040) were simulated under 10 treatments of nine scenarios. A simulation scenario (n=50) corresponded to one of three variations of springflow (random, high and low flow) and one of three variations in percentage of runoff entering the river (100, 50 or 30). The 10 treatments were variations on water quality: uncontaminated (1), contaminated by Cu (2), Zn (3), Cd (4), Cr (5), polycyclic aromatic hydrocarbons (PAH) (7), bifenthrin (8), carbaryl (9) and dicamba (10) and an additive affect of Cu, Cr, Cd, and Zn (6). Simulating ideal conditions, the average darter population from 2008-2040 was 54155+2969 (mean+SE) individuals. Contaminant treatments that caused a significant (p<0.001) decline in the population by 2040 under 100% runoff conditions were the all metal (650 plus/minus 640), Cu (3141 plus/minus 265), PAH (4621 plus/minus 475), Zn (6169 plus/minus 5406), and Cd (27987 plus/minus 6751) scenarios. With 50% runoff, the all metals (15740 plus/minus 5455), Cu (16815 plus/minus 6263), PAH (19675 plus/minus 995), and Zn (15585 plus/minus 3097) treatments simulated significantly lower populations (p less than 0.001). At 30% runoff, Cu (23976 plus/minus 6787), the all metal (25853 plus/minus 7404) and PAH (28167 plus/minus 1194) treatments decreased the population significantly (p less than 0.001). Over all scenarios, copper, zinc and PAHs caused >50% decline in the population. Assuming 100% or 50% of all San Marcos sub-basin runoff is directly entering USMR, there could currently be levels of Cu, Zn, and PAHs higher than what darters can withstand.Item New methods for quantifying and modeling estimates of anthropogenic and natural recharge : a case study for the Barton Springs segment of the Edwards Aquifer, Austin, Texas(2011-05) Passarello, Michael Charles; Pierce, Suzanne Alise, 1969-; Sharp, John Malcolm, 1944-; Cardenas, Bayani R.Increased population and recent droughts in 1996 and 2009 for the Barton Springs segment of the Edwards Aquifer have focused attention on groundwater resources and sustainability of spring flow. These springs serve as a local iconic cultural center as well as the natural habitat for the endangered Barton Springs salamander. In response to the potential compromise of these vulnerable groundwater resources, a two-dimensional, numerical groundwater-flow model was developed for the Barton Springs / Edwards Aquifer Conservation District and other governmental entities to aid in aquifer management. The objective of this study is to develop new methods of quantifying and distributing recharge for this model. The motivation for conducting this study includes the following: recent availability of more extensive data sets, new conceptual models of the aquifer system, and the desire to incorporate estimates of urban recharge. Estimates of recharge quantities and distributions for natural and artificial sources were implemented within this model to simulate discharge at Barton Springs and water-level elevations from January, 1999 to December, 2009. Results indicate that the new methods employed generated good agreement amongst simulated and observed discharge and water-level elevations (Root mean square error of 0.5 m3 sec-1 and 10.5 m, respectively). Additionally, these recharge calculations are decoupled from Barton Springs discharge which eliminates the circular logic inherent with the previous methodology. Anthropogenic, or artificial, recharge accounts for 4% of the total recharge between January, 1999 and December, 2009. Using observed data to quantify contributions from leaky utility lines and irrigation return flows, recharge estimates were completed with spatial and temporal resolution. Analyses revealed that on a month by month basis, anthropogenic contributions can vary from <1 to 59% of the total recharge. During peak anthropogenic recharge intervals, irrigation return flow is the most significant contributor. However, leakage from utility lines provides more total recharge during the study period. Recharge contributions from artificial sources are comparable to the mid-size watershed contributions over the ten-year analysis period. Urban recharge can be a critical source for buffering seasonal fluctuations, particularly during low flow periods. Outcomes are relevant for habitat conservation, drought response planning, and urban groundwater management.Item A new phase in water resource allocation : the case for groundwater markets in Texas(2013-05) Avioli, Lauren Faye; Oden, MichaelThis report explores the application of a market framework to allocating water resources, with a specific focus on groundwater resources in Texas. Water markets have been touted by economists as an efficient and effective means of reallocating a scarce natural resource and have been implemented in various forms across the western United States. This report discusses the characteristics of water markets that allow them to efficiently allocate water resources as well as the need for institutional oversight to address negative externalities, including environmental and third party impacts. A description of Texas law and regulation of groundwater resources is also given and analyzed in the context of establishing widespread groundwater markets in the state. Several case studies, both in Texas and in other western states, are also analyzed to determine best practices for the creation of a statewide system of groundwater marketing. The report concludes with several recommendations based on these case study analyses and in light of the current legal and regulatory obstacles to widespread water markets in Texas.Item Quantifying land cover in a semi-arid region of Texas(Texas A&M University, 2005-02-17) Peschel, Joshua MichaelChanges with land cover and land use are closely integrated with water and other ecological processes at the land surface. Nowhere is that more apparent than in the Edwards Aquifer region of southcentral Texas. The Edwards Aquifer contributing and recharge zones cover approximately 18,000 square kilometers in parts of 15 counties in Texas and includes San Antonio and Austin, the nation's eighth and nineteenth largest cities, respectively. Population growth within the counties that intersect the Edwards Aquifer contributing and recharge zones has taken place over the last two decades, with the logical translation being an expanded infrastructure. This implies that a greater amount of impervious surface coverage and other land cover changes have occurred. This work quantified the changes in land cover within the Edwards Aquifer contributing and recharge zones between the years 1986 and 2000. Increasing trends in impervious surface area and woodland growth were identified. Additionally, a new ArcView software tool was developed to process SSURGO soil data for use within the ArcView SWAT model. Hydrologic modeling for the Upper Sabinal River watershed, located within the Edwards Aquifer region, revealed that the high resolution SSURGO data produces different results when used in place of the existing STATSGO soils data. Finally, an index of urbanization was developed and evaluated to assist investigators in identifying potential areas of urbanization.Item Surface water recharge in karst : Edwards-Trinity Aquifers-Nueces River system(2015-05) Kromann, Jenna; Sharp, John Malcolm, Jr., 1944; Gary, Marcus O.; Johnson, Joel PThe karstic Edwards Aquifer is a primary source of water in south-central Texas for domestic, agriculture, and industrial uses. Significant recharge into the aquifer occurs as surface water streams, including the Nueces River, cross the Recharge Zone (RZ). Recharge models use data from two stream gauges, located above and below the RZ. These gauges are used to compute recharge into the aquifer; this may underestimate recharge volume because the actual water balance is complex. Synoptic gain/loss studies show that: flow rates change significantly as the river passes through extensive unconsolidated alluvium, gain/loss in reaches varies temporally, and recharge may be occurring in the Contributing Zone (CZ). From these synoptic studies, a 10-km reach of the Nueces River near Montell, TX, was identified that loses 100% of flow over the CZ during low stream flows. In this study reach, Candelaria Creek runs parallel to the dry segment of the Nueces River for 2.5 km; the creek contributes 52-64% of flow measured at the USGS recharge index gauge. The main sources of flow to the creek are two springs, hypothesized as possibly being sourced from: underflow from the Nueces River, a combination of Trinity Aquifer groundwater and river underflow, or solely groundwater from the Trinity Aquifer. To investigate recharge in the CZ and the source water for springs that contribute flow to Candelaria Creek, a variety of methods were used including: hydrograph and gain/loss analyses, potential evapotranspiration calculations, and interpretation of specific conductance, temperature, chemical, isotopic, and near surface geophysical data. The data suggest that the springs are likely sourced from both Nueces River underflow and Trinity Aquifer groundwater. Defining the source of the springs that contribute to Candelaria Creek is important to understand the complex water balance in the Nueces River and the role of underflow/storage in this system. It was found that underflow was a significant source of spring flow, but could not account for the total amount of spring flow; this suggests the Trinity Aquifer also contributes flow to the springs. A water balance estimates that recharge in the CZ at 6,213,048-9,814,814 m3 per year, which is between 0.9 to 2% of total recharge to the Edwards Aquifer and 4 to 11% of Nueces Basin recharge may be unaccounted for over the CZ during low hydrologic flow conditions. This water balance suggests that there is significant recharge occurring over the CZ and some recharge may be unaccounted for based on the current method used to calculate recharge.Item The water generation gap(2013-05) Phillips, Ariel Isaac; Dahlby, TracyFor thousands of years freshwater springs provided the foundations of human settlement in Texas, from Native Americans to Spanish missionaries to German immigrants. However, over the last generation in Texas – and across much of the United States and the rest of the world – water has become just another convenience of modern life, available at the turn of a handle or push of a button. But times are changing. In Texas a perfect storm is brewing as the population booms and water resources deplete, and many people believe water will soon overtake oil as the next big play in the state. Already there is a sustained effort by companies and investors to secure major water assets and rights. At the same time, almost paradoxically, Texans continue to overuse water for lush lawns, poorly suited agriculture, and overtaxed infrastructure without considering the long-term impacts of these habits. As recently as a generation ago, during the previous drought of record in Texas in the 1950s, most Texans either relied on rain for survival – for livestock or agriculture – or knew a family member that did. That connection to water has been all but lost over the last 50 years as reservoirs have brought reliable water supply to an increasingly urbanized population. Now flushing the toilet is as familiar as most people get with the water cycle. Sharlene Leurig, a young woman who is extremely passionate about water in both her professional and personal life, is both a throwback to a different Texas and a promising indicator of how Texans might come to grips with the new water future coming down the pipe. I follow Leurig on her quest to document springs across Texas while also meeting with veteran water experts who’ve spent their lives submerged in the issue.